Mevalonate kinase (EC2.7.1.36; ATP: mevalonate-5-phosphotransferase) is a cytosolic enzyme in the cholesterol biosynthetic pathway which catalyzes the phosphorylation of mevalonate to form mevalonate-5-phosphate. Holloway, P. W. et al., Biochem J. 104, 57-70 (1967). Although mevalonate kinase has been described in animals and plants, very little is known about its regulation. However, there is some evidence to suggest that the regulation of mevalonate kinase may be involved in the regulation of cholesterol biosynthesis. The activity of mevalonate kinase is inhibited by geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP), which are intermediates in the cholesterol biosynthetic pathway after mevalonate kinase. GPP and FPP inhibit mevalonate kinase activity by binding competitively at the ATP-binding site on the enzyme, and it has been postulated that mevalonate kinase activity may be regulated by feedback inhibition from GPP and FPP. See, Dorsey, J. K. et al., J. Biol. Chem. 243, 4667-4670 (1968). However, further studies are needed to determine if mevalonate kinase plays a regulatory role in the cholesterol biosynthetic pathway.
Furthermore, mevalonic aciduria, a genetic disease involving the cholesterol biosynthetic pathway, has recently been discovered. There are six reported cases of mevalonic aciduria, and the genetic disease is transmitted as an autosomal recessive trait. Subjects with this disease have extremely high levels of mevalonate in their plasma and urine, and cells from these subjects have less than 10% of the normal levels of mevalonate kinase activity. Hoffman, G. et al., New Engl. J. Med. 314, 1610-1614, (1986); Brown, M. S. et al., J. Lipid Res. 21, 505-517 (1980). Mevalonic aciduria may result from a mutation in the gene coding for mevalonate kinase. However, additional studies are needed to clearly identify the mutation(s) responsible for this genetic defect.
Thus, it is readily apparent that the need exists in the art for sources of human mevalonate kinase so that its role in the regulation of cholesterol biosynthesis may be ascertained. There is also a need for methods for the detection and study of the human genetic disease mevalonic aciduria.